Front sear for rifles



S. SCHIFF FRONT SEAR FOR RIFLES 0a. z8, y 1947-.

Filed May 5, 194e 5 Sheets-sheet 1 Oct. 28, 1947. s. scHlFF FRONT SEARFOR RIFLES Filed May 5, 1946 5 Sheets-Sheet 2 3 Shets-Sheet 5 s. sci-UFFFRONT SEAR FOR RIFLES oct. A28, 1947.

Filed May 5, 1946 Nm mw mw Patented Oct. 28, 1947 UNITED STATES PATENTOFFICE FRONT SEAR FOR RIFLES Sigmund Schiff, Cincinnati, Ohio, assignorto the United States of America, as represented by the Secretary vof War(Granted under the act of March 3, 1883, as amended April 30, 1928; 3700. G. 757) The invention described herein may be manufactured and usedby or for the Government for governmental purposes, without the paymentto me of any royalty thereon.

This invention relates to a breech block assembly for use with anautomatic gun of the type of the 20 mm. aircraft Weapon.

An object of the invention is to provide asturdy block of comparativelyfew parts and these so formed and arranged and cooperating to reduce toa minimum the likelihood of malfunctioning and adding to thelife of thegun and the facility of its operation.

The `block of the gun of the type mentioned is operated partly by gasrecoil means and partly by blowback means, that is to say, by a modicumof gas derived by the bore of the gun when the round is ired andblowback force of the round when the round is exploded.

The block comprises a main body portion and a slide slidably relatedthereto. The body portion is normally locked in battery position andrecoils in response to the blowback force of the explosion of the roundof ammunition for the purpose of extracting ejecting and feedingammunition after having been unlocked from battery position by the slide`in its initial rearward movement responsive to the gas derived from thebore `of the gun when the gun is fired, the slide also operating to cockthe firing pin against its spring upon such initial rearward movement,and to compress the slide returning springs preparatory to returning theslide to battery position wherein the firing pin is in position to beprojected to re the round to inaugurate another cycle, or cycles.

The improvements about to be described reside particularly in the searand ring pin, their construction and location relative to each other andto the slide element and in the modification of the slide and main bodyof the block for coaction with the sear and ring pin, and in theprovision of a spring for the ring pin independent of the recoil andcounterrecoil or drive spring, `assuring uniform extent of movement anduniform impact strength of the pin with respect to the round ,in thegun, thus eliminating the likelihood of misre and incidentmalfunctioning of the gun.

Ordinarily the sear is a spring-backed element engaging a notch in ahammer or iiring pin and released by a trigger to fire the round, therebeing no other function of the sear. In the present instance the searand firing pin are so constructed that they cooperate with each otherand with the slide and main body portion of the block in a radicallynovel manner, so far as I` am aware.

The sear may be described as a floating element, that is to say, it isnot attached to any other portion and is free to be rocked and/ordepressed and caused in its movements to assume successively, severalpositions relative to the firing pin and slide, notably among which isWhere the sear, after being released from the notch in the ring pin, isdepressed by the pin in its forward movement to unlock the slide topermit it to be moved rearwardly to unlock the main body portion. Thesear not only performs the oilice of a sear but serves as a lock toprevent the rebound of the slide relative to the main body portion ofthe block when the block returns to lbattery position, thus preventingthe slide from prematurely unlocking the body portion of the block atthe time of firing.

As stated at the outset, the block compresses two main portions. Thesewill hereinafter be designated as the body portion which is the partthat carries the sear, sear spring, firing pin, ring pin spring, recoil4and counterrecoil spring, and the sear releasing cam and extractor,some of which are constructed and arranged to coact intimately withparts carried by the other main part of the block which will bedesignated as the slide.

The receiver will be internally shaped to accommodate, guide and supportthe block in its reciprocations therein and to prevent lateral movementof the block, all as is customary in such structures. It is closed atits front end with exception of a threaded opening for the reception ofthe threaded portion of the gun barrel, and at its rear end it isprovided with the usual buffer device.

Other objects and advantages of the invention other than those statedwill become apparent from the following description.

In the drawings illustrating the invention:

Figure 1 is a longitudinal vertical section of the receiver and rearportion of the gun barrel, the block being shown in side elevation andin locked battery position, the ring pin being cocked;

Figure 2 is a longitudinal section of the receiver showing a portion ofthe gun barrel with the slide portion of the block removed, the lowerpart of the block and parts carried thereby or closely associatedtherewith, in plan;

Figure 3 is a view like Figure 1, with the body and slide inlongitudinal vertical central section showing the parts in batteryposition with the ring pin cocked;

Figure 4 is a fragmentary view of the forward end of the receiver andthe rear end of the barrel, the block parts and sear being in sectionand in the position they occupy at the time of firing;

Figure 5 Iis a View substantially like Figure 3, with the parts being ininitial recoil position;

Figure 6 is a transverse vertical section of the receiver and blockabout on the line 5 6 of Figure 1;

Figure 7 is a view on the line 'I-'I of Figure 1;

Figure 8 is a perspective view of the sear;

Figure 9 is a side elevation of the slide partly broken away to show therelation of the slide return springs (of which there are two) andmovable block yieldingly connecting the slide with the body portion ofthe block in their sliding movement relative to each other.

Figure 10 is a similar view of the body portion of the block, the searbeing-in section;

Figure 11 is a frontend view of Figure 9;

Figure 12 is a front end View of Figure 10;

Figure 13 is a fragmentary section of the forward end of the blockshowing the sear released and in position to be depressed by the ringpin in its forward movement under the influence of the ring pin spring;

Figure 14 is a similar view showing the parts in firing position, thefiring pin in its forward movement having levelled up the sear;

Figure 15 is a view similar tofFigure 14, the parts being in recoilposition and the sear in position to engage the sear notch to cock thepin;

Figure 16 is a similar view showing the firing pin cocked and in batteryposition;

Figure 1'7 is an inverted perspective View of the ring pin;

Figure 18 is a perspective View of the Sear spring;

Figure 19 is a detail perspective VView of the sear operating cam and aportion of the sear showing the formation of the cam whereby the lateralmovement of the cam produces a downward movement of the sear.

Referring to the drawings, the receiver is generally indicated by thenumeral I, which, as stated, is of usual construction, open at its topand bottom and having parallel side walls 2 and longitudinally extendinginternal top flanges 3 which embrace and guide .the upper portion pf thebreech block, and inwardly extending rails 4, the latter for supportingthe block assembly in its reciprocations in the receiver, as best shownin Figures 6 and 7.

Spanning the space between the side walls of the receiver and forming aportion thereof, is a key 5 which cooperates with a block lock, both ofwhich will be presently described in detail together with the manner oftheir cooperation with other parts of the assembly.

At the front of the receiver is a block 6 which threadedly receives thebarrel 'I provided with the usual cartridge chamber 8. The block 6 isformed with a central lug 9 into which is threaded the rear end of ashort guide rod I9 who-se front end extends into the gas cylinder sleeveII carried by the gun barrel. The rear end of the gas cylinder carries ayoke I2 whose arms straddle the breech portion of the barrel and carryrearwardly extending push rods I3 whose rear ends engage the forward endof the block slide to impart rearward movement thereto upon the rearwardmovement of the sleeve II, the sleeve being actuated by gas from a port(not shown) in the gun barrel upon the firing of the round, all as usualin guns of this type.

Reference is made particularly to Figures 9 and 10 in which I4designates the main body of the block, and I5 the slide, the relativepositions of the parts being such'that they would t accurately togetherif assembled. The general cross-sectional shape of the body portion andthe slide are shown in Figures 11 and 12 which are end elevations ofthose parts. The body portion I4 is formed with a central, longitudinalsemi-circular driving spring groove I6 on each side of which is a trackI 'I for sliding engagement with the downwardly facing track I8 of theslide I5. The groove extends throughout substantially the full length ofthe body portion, but is interrupted near its front end by a transverserecess I9, Figure 2, for the reception ci the novelly-shaped andnoVelly-arranged sear 29, shown best in Figures 2, 8 and 19. The frontend of the body portion I4 terminates in an upstanding wall 2l at therear of which is a continuation of the groove I6 and the tracks I'I,Figure 2. This continuation is of smaller radius than the groove I5 asindicated b-y I6 to conform to the radius of the front portion of thering pin. TheV wall 2l is apertured centrally as at 22 for the passageof the striker 23 ora firing pin 24 appearing in most 0f the views, andin inverted perspective in Figure 1'7. Numeral 25 designates the Searspring shown in its entirety in Figure 18. The spring is of the leafvariety and formed with a base piece 25 bent to form an upwardly andrearwardly extending lip 21, the base piece being secured in the bottomof the recess I9. The slightly curved free end of the spring engages theunderside of the sear and urges it bodily upward, but as will presentlyclearly appear, allows the sear to rock in the recess with the spring asa fulcrum, for cooperating with the firing pin 24 and slide I5. The searhas formed integrally at each corner, an upwardly extending lug 28bevelled forwardly and downwardly as at 28' and adapted tov enter theoppositely disposed notches 29, also bevelled as at 29', Figures 1 and9, for proper cooperating with said lugs, for a purpose that willappear.

There is a central recess 39 in the front edge ofthe sear presenting ashoulder for engagement with a specially formed part of the firing pin.The sear is further provided with side extensions 3I, Figures 2, 8 and19, provided with cam surfaces 32 for cooperating with cam surfaces 33of a spring-backed sear operating lever or trigger 34 pivotally mountedat 35 in a vertical recess 36, Figure 2, in the side wall of the bodyportion I4, the extensions 3| extending rearwardly to position to beengaged by the cam when actuated to release the sear. The rear of thesear body terminates in a sharp edge 31 which is bevelled downwardly andforwardly between the extensions 3| for engagement with the sear notchin the firing pin. The front edge of the sear is denitely bevelled asindicated at 38, Figure 8, to conform to the bevelled surfaces 39 of theinner wall of the recess I9, Figures 13 and 14. There is an abutment 40in the groove I6 between which and the cylindrical rear end 4I of thefiring pin is the ring pin spring 42 which is independent of a recoiland counterrecoil or driving spring 43 which is also seated in thegroove and contains a guide plunger 44 whose forward end engages theabutment 40, and which, with the spring 43, extends through the tubularportion 45 of the body portion I4, the plunger rod extending into theguide sleeve 44' which extends to the usual buffer mechanism (not shown)at the rear of'the receiver.

'Ihe firing pin 24 is shaped to form a flat bearing surface 46 on itsunderside terminating at its forward end in a sear notch 41 preferablyvinolining slightly downwardly and forwardly for engagement at times4with the edge 31 of the sear. The rear end 4I off the firing pin iscylindrical and has an easy sliding fit in the groove I 6, Vibut from 'apoint just forward of the sear notch the pin is reduced `in diameter toform 'a forwardly facing important shoulder 4'8 which cooperates withthe slide in its rearward movement tocock the pin. The forward reduced'end of the pin presents a definite rearwardly facing Vshoulder 49Vwhich engages the notch 3B in ythe front edge `of the sear, the spacebetween the sear notch and the shoulder 49 being enough to allow thefiring pin 'to be moved backward far enough to let the rear edge of thesear engage the notch in the pin.

The mechanism for locking the body portion I4 in battery position ischaracteristic of the 20 mm. type of gun. It 'comprises a transverserecess 5i! in whose front wall there is a transverse semi-circulargroove 5I in which is rockably received the semi-circular end of a blocklock 52 that ffolds into the recess to unlock the block (Figure 5) andpermits it to move rearwardly, but arranged to engage 'the notch 53 inthe key 5 (Figures 1 and 3) t'o lock the body portion `I4 in batteryposition.

The lock 52 is provided with two oppositely disposed upwardly andforwardly inclined projections 54 which are arranged to engage upwardlyand forwardly yfacing inclined cam faces 55 made in the opposite sidewalls of the rear end of the slide,the projections cooperating with thecam faces to cam the lock 52 upwardly and out of engagement with thenotches 53 of the key 5, so that the lock clear the key to unlock thebody portion VI4 and permit it to be moved rearwardly by blowbackpressure.

The foregoing description has been Vvfor the most part of the lower bodyportion I4 of the block, and the parts carried thereby. VReference isnow made tothe Figures9 and 11. The roof 56 of the 'slide I5 is providedwith a central semicircular groove 51 between 'the tracks I8 which matchwith the groove I6 in the body `I4 for the greater part of the length ofsaid, groove I6, so that when the block is assembled there is formed acylindrical bore :for the reception of the upper portion of the drivingspring 43, abutment 4B, firing spring Y42 and a portion of the firingpin 24. The groove 51 is reduced in radius at its forward end to form ashort groove 51 corresponding with the groove II in the lower bodyportion of the block. This reduction in the radius of the grooveshoulder 51" against which the front end of the firing pin engages attimes, for a purpose that will later appear.

Just in advance of the cam faces 55 in Figure 1, in the side walls oithe slide, there are two oppositely disposed elongated recesses 58,Figures 1 and 6, in which are slidably mounted oppositely disposeddownwardly extending lugs 55 to each of which is attached a guide rod 59within thel coils of slide return springs 5I with one end abuttingagainst a lug 59 and the other against an abutment in its recess, therearward movement of the lugs being limited by the rear ends of therecesses.

A plate, such as 62, Figures 1, 6, 9 and 11, is sein the slide forms adefinite lliV cured Vto each side of the wall of the slide, as forinstance, by screws 63. The lower side of the plates are bent inwardlytoform iianges 53' which extend for about one half of the length of therecesses to completely house the guide rods and return springs, but arecutaway for a suitable distance in advance of the lugs 59 for thepassage of thelugs and to permit them to have the necessary slidingmovement in their recesses in performing their functions in cooperationwith two oppositely disposed notches 64, Figure 10, in the body portionI4, their functions being to compress the spring EI on the rearwardstroke of the slide under the influence of the push rods actuated by gasfrom the gun barrel, and the return of the slide to its normal position.

The angle of the bevel 25' of the notches `29 in theslide I5 is suchwith respect to the bevel 28 of the sear lugs 2B that the tendency ofthe slide to rebound upon reaching battery position will not besufficient to disengage the lugs from the notches, but upon theapplication of sufficient manual force exerted upon the slide, theselugs may be retracted as becomes necessary to initiate ammunition feed.

As shown in Figures 3 and 4, there is the usual extractor 55 rockablymounted on the body -portion I4, there being the usual extractor spring66 tending to hold the upper ends of the extractor elevated.

Operation-Reference is made to Figures 1, 2 and 3, and more particularlyto Figures 13, 14, 15 and 16, which latter gures are somewhat enlargedfragmentary sections of the block in the neighborhood of the sear,firing pin and sear spring, showing various positions the sear, firingpin and slide assume at dilerent stages of the cycle of operation of theblock. In Figure 16 the firing pin is cocked and the gun ready to be redwith the edge 31 of the sear in the sear notch 41. The trigger 34,Figures 2 and 19, is rocked inwardly either manually or otherwise sothat its cam 33 engages the cam surface 32 of the sear depressing itsrear portion, Figure 13, the sear meanwhile fulcruming on its spring 25and smoothly riding against the correspondingly shaped rear ends 39 ofthe short track sections flanking the short groove I6 in the bodyportion I4 of the block. The depression of the rear portion of the searto the positions shown in Figure 13 `permits the flattened portion 46 ofthe firing pin, under the influence of its spring 42, to ride upon andatten out the sear and simultaneously withdrawing the sear lugs 2S fromthe notches 23 in the slide, the pin continuing its movement to theiiring position shown in Figure 14. Upon ring a round the gas from thegun barrel causes the push rods I3, Figures 1 and 3, to move the sliderearwardly. The slide in moving rearwardly brings the shoulder 51 of theslide into engagement with the shoulder 48 of the firing pin, carryingthe pin back with the slide to the recoil position shown in Figure 15wherein the sear spring 21 acts to bodily elevate the sear to positionto enter the notch in the firing pin counterrecoil. During the initialrearward movement of the slide the body portion I4 can not move and ismomentarily held in battery position being locked by the block lock 52in engagement with the key 5, Figures 1 and 5. However, when theforwardly facing cam surfaces of the projections 54 of the lock engagethe rearwardly facing cams 55 of the slide block lock, the lock will becammed upwardly into its recess, clearing the key 5 and unlocking thebody portion of the block from the 7 receiver.` The slide and bodyportion are now free to move rearwardly together on recoil responsive tothe blowback force of the explosion of the round, against the restraintof the driving or recoil. and counterrecoil spring G3, which With thebuffer spring (not shown) returns them together to battery position,when the lugs 28 of the sear enter the notches 29 in the slide andprevent the rebound of the slide against the then released slide returnspring 6l when the slide and bolt reach battery position.

When the gun is fired by remote control, a solenoid arrangement may beemployed such as is indicated by the numeral 65, suitably attached tothe outer wall of the receiver. In the present case the trigger 34ywould be operated by the solenoid plunger 66 whose operation is thereverse of the ordinary plunger in that the plunger is projected orpushed against the trigger rather than being pulled to release the sear.

I claim:

1. A breech block reciprocable in recoil and counterrecoil and for usein automatic machine guns, comprising a body portion and a slide mountedon said body portion and associated therewith for joint and independentrelative movement, means for initiating recoil of said body portion andslide, means for locking the body portion in lbattery position at thetime of firing, said slide being constructed and arranged to unlock thebody portion upon initial rearward movement of said slide, a sear insaid body portion, means carried partly by the sear and partly by theslide cooperating to lock the slide in battery position along with saidbody portion when in :dring position, a spring-backed ring pincontroll-ed by the sear, means for operating the sear to release thefiring Din and at the same time unlock the slide from said body portionto permit the slide to move rearwardly independently of said bodyportion. Y

2. A breech block reciprocable in recoil and counterrecoil and for usein automatic machine guns, comprising a body` portion and a slidemounted on said body portion for joint` and independent movement, meansfor initiating recoil oi said body portion and slide, means for lockingthe body portion in battery-position at the time of firing, said slideconstructed and arranged to unlock said body portion upon` initialrearward movement of the slide, va transverse recess adjacent theiorward end of said body portion, a sear in said recess, a sear springin said recess supporting said sear and serving as a ful- Crum for theoperative movements of the sear,

means carried partly by the sear and partly by the slide for cooperatingto lock the slide in bat-' tery position along with the body portion, a

spring-backed ring pin controlled by the sear, and means for operatingthe sear to release the iiring pin and at the same time unlock the bodyportion from the slide to permit the slide to move rearwardlyindependently of said body portion.

3. A breech block reciprocable in recoil and counterrecoil and for usein automatic machine guns, comprising a body portion and a slide mountedfor joint independent relative movement, means for initiatingvrecoil ofsaid body portionv and slide, means for locking the body portion inbattery position at the time of ring, said slide being constructed andarranged to unlock said body portion upon the initial rearward movementof the slide, a transverse recess adjacent the forward end of the bodyportion, a sear in said recess, a sear spring in said recess supportingthe sear and serving as a fulcrum for the sear in its operativemovements, lugs carried by the sear, means carried by the slidecooper-ating with the lugs to lock the slide in battery position alongwith said body portion at the time of ring, a firing pin slidablebetween said body portion and slide and spanning said recess andoverhanging the sear, said firing pin being formed with an undercutportion having a notch therein engaged lby the sear, said firing pinbeing further provided with a shoulder arranged to be engaged by theslide upon its initial rearward movement to cock the firing pin, aspring carried by said body portion in engagement with the ring pin andindependent of the recoil and counterrecoil springs of the weapon, andmeans for operating the sear to release it from the ring pin and tosimultaneously unlock said body portion from the slide to permit therearward movement of the slide independently of said body portion. v

4. The invention of claim 3 characterized in that the means carried bythe slide cooperating with the lugs on the sear comprises oppositelydisposed recesses in the slide entered by said lugs, and that the searis provided with a rearward extension having a cam surface thereon, andthat the means for operating the sear to release the iiring pin andunlock the body portion of the block comprises a trigger pivoted to saidbody portion and provided with a cam surface cooperating with the camvsurface of the sear extension to depress the sear upon the inwardmovement of the trigger.

SIGMUND SCHIFF.

